Electrical-device adhesive barrier

Abstract

A circuit-board-assembly includes a printed-circuit-board, an integrated-circuit-die, a ball-grid-array, a barrier-material, and an adhesive-material. The printed-circuit-board includes a mounting-surface that defines a plurality of contact-pads and a continuous-trace that interconnects a selected-group of the contact-pads. The integrated-circuit-die includes an electrical-circuit having a plurality of solder-pads. The ball-grid-array includes a plurality of solder-balls interposed between the contact-pads and the solder-pads. The plurality of solder-balls establish electrical communication between the electrical-circuit and the contact-pads. The barrier-material is located between a string of solder-balls that are attached to the selected-group of the contact-pads to create a barrier. The barrier segregates an underfill-region from a non-underfill-region between the printed-circuit-board and the integrated-circuit-die. The barrier is in direct-contact with the string of the solder-balls, the integrated-circuit-die, and the continuous-trace. The adhesive-material is in direct contact with a portion of the underfill-region and the barrier prevents the adhesive-material from encroaching upon the non-underfill-region.

We claim: 
     
       1. A circuit-board-assembly, comprising:
 a printed-circuit-board that includes a mounting-surface that defines a plurality of contact-pads and a continuous-trace that interconnects a selected-group of the contact-pads; 
 an integrated-circuit-die that includes an electrical-circuit, said integrated-circuit-die having a plurality of solder-pads; 
 a ball-grid-array that includes a plurality of solder-balls interposed between the contact-pads and the solder-pads, said plurality of solder-balls establish electrical communication between the electrical-circuit and the contact-pads when the circuit-board-assembly is assembled, 
 a barrier-material located between a string of solder-balls that are attached to the selected-group of the contact-pads to create a barrier that segregates an underfill-region from a non-underfill-region between the printed-circuit-board and the integrated-circuit-die, whereby the barrier is in direct-contact with the string of the solder-balls, the integrated-circuit-die, and the continuous-trace; and 
 an adhesive-material in direct contact with a portion of the underfill-region, whereby the barrier prevents the adhesive-material from encroaching upon the non-underfill-region. 
 
     
     
       2. The circuit-board-assembly in accordance with  claim 1 , wherein the barrier-material is a conductive-solder. 
     
     
       3. The circuit-board-assembly in accordance with  claim 2 , wherein the string of solder-balls are metallurgically bonded to the solder-pads and the continuous-trace, and wherein the conductive-solder is metallurgically bonded to the solder-balls and the continuous-trace. 
     
     
       4. The circuit-board-assembly in accordance with  claim 3 , wherein the barrier provides a ground-path for the electrical-circuit. 
     
     
       5. The circuit-board-assembly in accordance with  claim 3 , wherein the electrical-circuit is a monolithic-microwave-integrated-circuit. 
     
     
       6. The circuit-board-assembly in accordance with  claim 5 , wherein the non-underfill-region contains solder-balls that propagate radio-frequency-signals between the printed-circuit-board and the integrated-circuit-die. 
     
     
       7. The circuit-board-assembly in accordance with  claim 1 , wherein the barrier-material is an epoxy. 
     
     
       8. The circuit-board-assembly in accordance with  claim 7 , wherein the epoxy is electrically-conductive. 
     
     
       9. The circuit-board-assembly in accordance with  claim 1 , wherein the adhesive-material is an epoxy. 
     
     
       10. The circuit-board-assembly in accordance with  claim 1 , wherein the integrated-circuit-die is rectangular and the adhesive-material is located beneath corners of the integrated-circuit-die. 
     
     
       11. A circuit-board-assembly, comprising:
 a printed-circuit-board that includes a mounting-surface that defines a plurality of contact-pads and further defines a selected-group of the contact-pads; 
 an integrated-circuit-die that includes an electrical-circuit, said integrated-circuit-die having a plurality of solder-pads; 
 a ball-grid-array that includes a plurality of solder-balls interposed between the contact-pads and the solder-pads, said plurality of solder-balls establish electrical communication between the electrical-circuit and the contact-pads when the circuit-board-assembly is assembled, 
 a barrier-material located between a string of solder-balls that are attached to the selected-group of the contact-pads to create a barrier that segregates an underfill-region from a non-underfill-region between the printed-circuit-board and the integrated-circuit-die, whereby the barrier is in direct-contact with the string of the solder-balls, the integrated-circuit-die, and the printed-circuit-board; and 
 an adhesive-material in direct contact with a portion of the underfill-region, whereby the barrier prevents the adhesive-material from encroaching upon the non-underfill-region. 
 
     
     
       12. The circuit-board-assembly in accordance with  claim 11 , wherein the solder-balls are metallurgically bonded to the solder-pads and the contact-pads. 
     
     
       13. The circuit-board-assembly in accordance with  claim 12 , wherein the plurality of the solder-balls included in the barrier provides a ground-path for the electrical-circuit. 
     
     
       14. The circuit-board-assembly in accordance with  claim 12 , wherein the electrical-circuit is a monolithic-microwave-integrated-circuit. 
     
     
       15. The circuit-board-assembly in accordance with  claim 14 , wherein the non-underfill-region contains solder-balls that propagate radio-frequency-signals between the printed-circuit-board and the integrated-circuit-die. 
     
     
       16. The circuit-board-assembly in accordance with  claim 11 , wherein the barrier-material is an epoxy. 
     
     
       17. The circuit-board-assembly in accordance with  claim 16 , wherein the epoxy is electrically-conductive. 
     
     
       18. The circuit-board-assembly in accordance with  claim 11 , wherein the adhesive-material is an epoxy. 
     
     
       19. The circuit-board-assembly in accordance with  claim 11 , wherein the integrated-circuit-die is rectangular and the adhesive-material is located beneath corners of the integrated-circuit-die.